Distributed control systems (DCS) are highly adaptable and reliable, enabling the monitoring and control of process parameters through software programming, thus automating the production process. Due to their powerful hardware configuration, DCS systems can directly process signals from primary instruments in the production field, such as Pt100 thermocouple temperature measurement signals, K-type thermocouple temperature measurement mV signals, pulse switching signals, and standard voltage and current signals. However, a significant issue arises: if interference signals are introduced during transmission of process parameter measurement signals from the field, the DCS system itself will struggle to suppress them, requiring external measures to address the problem. This article describes methods for handling faults caused by abnormal Pt100 thermocouple temperature measurement signals. 1. Troubleshooting for Abnormal Thermocouple Temperature Measurement Signals in the Coal Mill System Our plant's coal mill system experienced successive abnormal temperature display faults in the bag filter dust hopper and the coal mill bearing. The symptom was irregular temperature jumps on the CRT display in the central control room. On-site inspection revealed that the temperature measuring elements were normal, and the resistance values ​​measured at the PC station relay terminals using a DT-890C digital multimeter corresponded to the actual temperatures. We implemented measures such as replacing the thermocouples, checking the shielding and grounding of the temperature measurement signal transmission cable, and changing the PC signal processing channel, but none of these measures were effective. To find the cause of the fault, we laid a new cable, but the problem persisted. After comparative testing and analysis, we concluded that interference signals were mixed into the temperature measurement signal. Therefore, we adopted the following solutions: 1.1 Changing the Signal Grounding Method: Thermocouple temperature measurement signals typically use a three-wire connection method, employing a KYVRP4×1.5 shielded cable to lead to the CCF relay cabinet in the DCS field station PC room. The cable is shielded and grounded inside the relay cabinet. The solution is to connect the B and b terminals of the Pt100 thermocouple to the cable shield at the relay cabinet terminal, introducing the interference signal to the ground. This method eliminates the interference signal, allowing the computer temperature display to return to normal. 1.2 Changing the signal transmission method: A Pt100 thermocouple temperature converter can be installed on-site or in the PC room of the field station to convert the Pt100 resistance signal into a standard DC 4-20mA signal. The computer input signal channel can be changed accordingly. This method can also eliminate interference generated during signal transmission, allowing the computer temperature display to return to normal. Because the DC 4-20mA signal has very strong anti-interference capability, the installation location of the temperature converter can be determined according to the actual site conditions, but it is best to choose indoor installation. The disadvantage of this method is that it increases equipment investment and requires a power supply for the converter. 2 Handling of abnormal temperature in the thin oil station of the cement mill main motor: 4 Due to a major overhaul, the main motor of our cement mill was replaced with a new motor, and the bearings are lubricated with thin oil. Accordingly, a thin oil lubrication station was added. The oil station has four temperature measuring points: lubricating oil tank temperature, heating oil temperature, supply oil temperature, and return oil temperature. After installation and commissioning, the temperature measuring system, heating control, and oil pumps of this thin oil station were functioning normally and it was put into operation. When the cement mill system was ready to start production, abnormal temperature displays occurred at the oil tank, supply oil, and return oil temperatures after the system's fans and other equipment were started. However, the heating oil temperature was unaffected due to the low ambient temperature and the heater's operation keeping the oil temperature high. The fault was that the temperature display on the central control room CRT monitor fluctuated irregularly between -30°C and +30°C. On-site measurements using a DT-890C digital multimeter showed no fluctuation in the resistance of the thermocouples. Replacing the computer signal channel did not improve the situation. Since it was discovered during installation that the transmission wires from the temperature sensing element to the field junction box were using ordinary, unshielded wires, it was decided to directly connect the connecting cable from the PC room to the field to the temperature sensing element terminals. The temperature display on the central control room CRT then returned to normal. Two hours later, when the main motor of the mill was started, the aforementioned temperature returned to zero again, fluctuating erratically between 0 and +30°C. Due to time constraints, we decided to take emergency measures by connecting the shield of the connecting cable to terminals B and b in the PC room. The temperature displays returned to normal, and the cement mill started normally. The main motor lubrication station is responsible for supplying lubricating oil to the front and rear bearings of the main motor. If the lubricating oil temperature measurement is abnormal, the main motor cannot be started; otherwise, the main motor bearings will not be effectively protected, potentially leading to a major accident. The main motor can only be started after the fault has been eliminated. Due to time constraints, a quantitative analysis of this fault could not be performed, but it is certain that this fault was caused by interference signals. 3. Handling Abnormal Temperature of the Vertical Shaft of the Raw Material Mill Classifier The vertical shaft of our raw material mill classifier is a product of the German company Humboldt. Three bearing temperature detection points (upper, middle, and lower) are designed according to the vertical shaft installation position. The CRT display on the control panel in the central control room shows the temperatures RT50MA, RT50MB, and RT50MC Sepa Bear Temp. Under normal operating conditions, the temperature detected by RT50MA is around 69℃, RT50MB around 78℃, and RT50MC around 94℃. According to equipment protection requirements, the bearing alarm temperature H1 is set to 125℃, and the shutdown protection temperature H2 is set to 135℃, with H2 serving as one of the interlocking shutdown conditions for the classifier. Since May 2000, under normal production conditions and equipment operation, RT50MA alarms have suddenly occurred, sometimes H1 alarms, sometimes H2 alarms, but then the system returns to normal. When an H2 alarm occurs, the instantaneous temperature reading exceeds 135℃, causing the classifier to trip, and subsequently the raw material mill system to shut down. Inspection of the thermocouples and wiring revealed no problems. Connecting the shield of the transmission signal cable to pins B and b of RT50MA also failed to eliminate the fault. Troubleshooting: A temperature converter was installed to convert the resistance signal into a DC 4-20mA standard signal, which was then input into the corresponding signal channel of the DCS system. This resolved the RT50MA temperature detection malfunction. The temperature converter was installed in a location with good external environmental conditions; we installed it in the CCF relay cabinet of the DCS field PC station. Subsequently, RT50MB and RT50MC also experienced the same fault. After checking the thermocouples and wiring and finding no problems, we used the same method to resolve the fault. In August, during the restart of our plant's equipment after maintenance, the classifier lubricating oil temperature RT-51 suddenly triggered an H2 alarm, causing the classifier to fail to start due to unmet startup conditions. We immediately inspected the equipment but found no problems. The temperature then returned to normal, and the temperature trend was similar to that of RT50MA. We immediately implemented the above method to resolve the issue, allowing the raw material mill system to start smoothly. 4. Conclusion Electromagnetic compatibility is a prominent and important issue in industrial and mining enterprises. Automatic detection mainly involves weak electrical signals, which are highly susceptible to electromagnetic interference during signal transmission. Due to factory limitations, these interferences cannot be monitored in real time, which makes it difficult to solve the interference problem. However, when conditions permit, the cable routing and distribution should be rationalized, that is, strong and weak cables should be laid in layers, and if necessary, the weak signal cables should be shielded for protection, which is an important anti-interference measure.